Skeletal muscle plasticity after hemorrhagic stroke in rats: influence of spontaneous physical activity.

OBJECTIVE: The aim of this study was to determine the contribution of spontaneous post-stroke physical activity to skeletal muscle plasticity after stroke. DESIGN: A randomized controlled study was conducted of 24 young adult male Sprague-Dawley rats assigned to three experimental groups: (1) STR-hemorrhagic stroke in the right caudoputamen; (2) SHAM-procedural control; and (3) CONT-no intervention (n = 8/group). Neurologic testing was performed before and 2 wks after stroke. Spontaneous physical activity was monitored five nights per week for 1 wk preoperatively and 2 wks postoperatively. Two weeks after stroke induction, bilateral soleus and tibialis anterior muscles were harvested. Myofiber cross-sectional areas were determined, and fiber typing was performed with immunohistochemistry. RESULTS: STR animals demonstrated neurologic deficit in the contralesional hindlimb 2 wks after stroke. Quantity of spontaneous physical activity did not differ between groups within each of the week-long study intervals. No significant difference was found in fiber types or cross-sectional areas in the soleus muscle of STR vs. CONT groups. However, the tibialis anterior muscle of the contralesional hindlimbs of the STR animals showed atrophy in 2x and 1 + 2x myofibers, as well as type 1 hypertrophy. CONCLUSIONS: Skeletal muscle adaptation occurs by 2 wks post-stroke in this model. It is muscle specific and appears to be influenced by factors other than spontaneous post-stroke physical activity.